The growth in the population of several of what have been the fastest-growing U.S. states – Arizona, Florida and Nevada, particular – is slowing as fewer Americans are moving there. The Census Bureau's annual estimate of state population changes cover the 12 months ending July 1, 2007. They also show that people continue fleeing the Midwest -- especially Michigan, one of two states to lose people – and that the Mountain states in the West continue to post large population gains as people arrive from California and elsewhere.